Organic thiol metal-free stabilizers and plasticizers for halogen-containing polymers

ABSTRACT

Organic thiol compounds are disclosed which can be utilized to plasticize and stabilize halogen-containing polymer compositions, especially poly(vinyl chloride) compositions. Compounds of the present invention are utilized in polymers normally susceptible to deterioration and color change, which typically occurs during processing of the polymer or exposure to certain environments.

FIELD OF THE INVENTION

[0001] The present invention relates to organic thiol compounds and thepreparation thereof. The organic thiol compounds can be utilized toplasticize and/or stabilize halogen-containing polymer compositions,especially poly(vinyl chloride) compositions. The compounds of thepresent invention are ideally utilized in polymers normally susceptibleto deterioration and color change which can occur during processing ofthe polymer or exposure of the polymer to certain environments andsurprisingly also serve as excellent plasticizers.

BACKGROUND OF THE INVENTION

[0002] It is well known that chlorine-containing resins, particularlypoly(vinyl chloride) polymers and copolymers, are unstable to heat andlight and that the physical properties thereof are degraded uponexposure thereto. This degradation is typically manifested bydevelopment of or change in color. It is particularly noticeable inunstabilized polymers, i.e., polymers which do not contain stabilizers.Degradation or discoloration during processing is particularlyundesirable in clear or lightly colored plastics. Therefore, it isdesirable to prevent or inhibit the discoloration of plastics duringprocessing so as to achieve useful products free of discoloration.

[0003] In order to minimize the discoloration and deterioration ofvarious halogen-containing polymers such as vinyl chloride polymers andcopolymers, various stabilizers such as lead-, cadmium-, and tin-basedstabilizers have been developed and utilized. However, in recent yearsenvironmental pollution caused by the toxicity of the heavy metalresidues and ecological considerations have stimulated furtherevaluation of such compounds and generated a search for alternativeapproaches.

[0004] Various compounds have been proposed for use in stabilizinghalogen-containing polymers:

[0005] U.S. Pat. No. 3,928,285 to Gough et al. relates to a synergisticstabilizer composition comprising an organotin borate and an organicthiol.

[0006] U.S. Pat. No. 4,948,827 to Christidis relates to a thiophenol,prepared by reduction of tertiary butyl-4-toluenesulfonyl-2-chloridewith the zinc-sulfuric acid couple, which reportedly can be used as astabilizer for vinyl chloride polymers, as a chain-transfer agent, andas a peptizer.

[0007] European Patent Application No. EP 0 890 608 A2 relates to bothflexible and rigid vinyl chloride polymer compositions incorporating alatent mercaptan-containing heat stabilizer which are reportedlysubstantially free from the offensive odor typically associated withmercaptans and are protected during processing by the degradationproducts of the latent (i.e., blocked) mercaptan, which include a freemercaptan. The free mercaptan thus released reportedly enhances theactivity of metallic-based heat stabilizers such as zinc carboxylatesand organotin carboxylates and mercaptides in the polymer composition.Other products of the degradation are believed to include carbocationsof the blocking moiety which are stabilized by a molecular structure inwhich the electron deficiency is shared by several groups. The latentmercaptan comprises a 2-S-(tetrahydropyranyl)thioalkanol or a carboxylicacid ester thereof.

[0008] European Patent Application No. EP 0 945 484 A1 relates tocompositions comprising halogen-containing polymers such as PVC resinswhich are reportedly stabilized against heat by a synergisticcombination of a free mercaptan and a metal-based stabilizer and/or aLewis acid such as zinc chloride.

SUMMARY OF THE INVENTION

[0009] Organic thiol compounds and routes for their preparation aredisclosed herein. The organic thiol compounds of the present invention,when blended with a halogen-containing polymer such as poly(vinylchloride) or derivatives thereof, provide numerous functions whichinclude serving as plasticizers, stabilizers, and dehydrochlorinationretarders. The organic thiol compounds of the present invention have asubstantially reduced or even lack a characteristic odor typicallyassociated with thiol compounds.

DESCRIPTION OF THE PREFERRED EMBODIMENT

[0010] The organic thiols of the present invention are aromaticcompounds having at least one sulfhydryl group attached either directlyor indirectly to an aromatic ring. The aromatic compound may contain oneor more aromatic rings and at least one sulfhydryl substituent, as wellas other groups such as an ester group, and the like. The organic thiolscan generally be described by the formula:

[0011] wherein R¹ and R², independently, comprise straight chain orbranched alkyls having from 1 or 2 to about 15 carbon atoms, andpreferably from about 4 to about 15 carbon atoms, or an aromatic or asubstituted aromatic having from about 6 to about 15 carbon atoms andwherein, independently, n is either 0, 1, 2, or 3, m is either 0, 1, 2,or 3, and p is either 0, 1, 2, or 3, with the proviso that m+n+p=6 orless. It is to be understood that when, independently, m, n, and/or pare greater than 1, the individual repeat groups are each attached to adifferent carbon atom on the benzene ring.

[0012] Independent exemplifications of R¹ and R² are 2-ethylhexyl,isooctyl, isodecyl, benzyl and butyl.

[0013] Examples of compounds which can be formed from the above formulainclude:

[0014] The various compounds of the above-disclosed general formulawherein m=0 can be synthesized substantially as follows. In a firststep, a desired amount of an hydroxy aromatic acid is placed in areaction vessel together with a large molar excess of an alcohol havingfrom 1 to about 3 carbon atoms, preferably methanol or ethanol. Fromabout 0.05 to about 0.5 mole, per mole of the starting acid, of a verystrong acid, i.e., one having a concentrated pH of at least 1 to about3, such as H₂SO₄, para-toluenesulfonic acid, or hydrochloric acid, isadded to the mixture, and the mixture is then heated either under air orpreferably under inert conditions, such as under nitrogen, generally tothe reflux temperature of the alcohol, for a sufficient length of timeuntil the reaction is complete, a condition which can be establishedthrough periodic analysis.

[0015] The hot solution is then poured into a quantity of ice water.Then, the precipitate is filtered off and washed on the filter until thepH of the wash liquid is neutral. The filtered product is then dried togive an hydroxy aromatic ester, which can be purified further byconventional methods, if desired.

[0016] A desired amount of the above-noted ester is added to a reactionvessel along with an N,N-dialkylthiocarbamoyl halide such asN,N-dimethylthiocarbamoyl chloride (about 1-3 moles per mole of ester),a base such as DABCO (about 1-3 moles per mole of ester), andN,N-dimethylformamide (about 1-3 liters per mole of ester). The mixtureis stirred at room temperature (e.g., 15° C. to about 30° C.) for asuitable reaction time, and a suitable quantity of water is then addedto induce precipitation of a solid which is filtered off and washed onthe filter until the pH of the wash liquid is neutral. The resultingsecond step intermediate product (the corresponding O-substitutedN,N-dimethylthiocarbamate) is subsequently dried.

[0017] The second step intermediate product is transferred to a suitablereaction vessel and heated preferably in an oil bath or the like to atemperature from about 180° C. to about 250° C. and desirably from about220° C. to about 235° C. until the reaction is complete, generally inabout 20 minutes to about 2 hours. Then, after cooling to about 60° C.to about 90° C., the reaction vessel is purged with nitrogen or otherchemically unreactive gas, and an aqueous solution of a base such asNaOH or KOH is subsequently added in an amount that is at leastsufficient to cause hydrolysis of the thiocarbamate and ester groups.The mixture is heated under reflux to induce complete reaction and thencooled to room temperature and acidified to a pH generally less than 4in any manner such as with a 10 percent aqueous solution utilizing anacid as stated above. The recovered mercapto acid product from the thirdstep is washed with suitable quantities of water and dried, preferablyunder a vacuum.

[0018] In the final step of the synthesis, the intermediate product fromthe third step is added to a reaction vessel equipped with a suitablestirring apparatus, a water separator, and a reflux condenser, alongwith an alkyl alcohol having from 1 to 15 carbon atoms in an amount fromabout 1 to about 2 molar equivalents per carboxyl group in the mercaptoacid, benzene or other suitable entraining agent for water (about 0.5 to2 L per mole of mercapto acid), and a strong acid (about 0.1 to 0.3 moleper mole of mercapto acid) as defined above. The mixture is heated tothe reflux temperature for a sufficient time to induce extensivereaction, typically approximately three hours, or until all the solid isdissolved. The solution is cooled to room temperature and poured intoice water, and the organic layer is washed in succession with a NaHCO₃or Na₂CO₃ solution and water. The organic layer is dried over a dryingagent such as anhydrous MgSO₄. The dried solution is decolorized withactivated carbon, filtered, and distilled to remove the benzene andother volatile impurities. The final product is generally an oil or lowmelting solid having a structure defined by the general formula of thepresent invention.

[0019] When m in the general formula is unequal to 0, the HSR²OOC groupsof the thiols of this invention can be introduced by the directesterification of COOH groups with thioalkanols (HSR²OH), using methodsthat are well-known to those skilled in the art. For example, compound11 in which R² is —(CH₂)₆— has been prepared by the esterification ofisophthalic acid with two molar equivalents of 6-mercapto-1-hexanol inthe presence of a catalytic amount of concentrated H₂SO₄.

[0020] Bis(2-ethylhexyl) 5-mercaptoisophthalate is one such compoundwhich is disclosed by the general formula of the present invention whenn is 1, m is 0, p is 2, and R¹ is 2-ethylhexyl, and is also shown asspecific formula 4. The synthetic route disclosed hereinbelow forpreparation of the bis(2-ethylhexyl) 5-mercaptoisophthalate compound isbased in part on a Newman-Kwart reaction, as in the general routedescribed above.

[0021] Bis(2-ethylhexyl) 5-mercaptoisophthalate Can be Synthesized asFollows:

[0022] To a 1-L round-bottom flask equipped with a magnetic stirring barwere added 187.8 g (1 mol) of 5-hydroxyisophthalic acid commerciallyavailable from Aldrich (purity approximately 97%) and 500 mL (12.3 mol)of methanol. After the addition of 28 mL of concentrated H₂SO₄, themixture was heated to the reflux temperature and stirred under refluxfor 4 hours. The hot solution was poured into 500 mL of ice water. Then,the white solid product was filtered off and washed on the filter withseveral portions of water until the pH of the wash liquid was neutral.The product was dried under vacuum, preferably at 60° C. overnight, togive 206.8 g of dimethyl 5-hydroxyisophthalate. Testing on thecomposition revealed the following data: mp 164-166° C.; GC purity>99%;yield 98.2%; ¹H NMR (in CDC₃+DMSO-d₆w/TMS, ppm): 3.68 (s, 6H, OCH₃),7.45 (s, 2H, CH), 7.89 (s, 1H, CH), 9.35 (broad, 1H, OH); {¹H}¹³C NMR(in CDCl₃+DMSO-d₆w/TMS, ppm): 51.92 (OCH₃), 120.50 (C4, C6), 121.10(C2), 131.15 (C1, C3), 157.36 (C5), 165.85 (COOR); ¹H-¹³C NMR (inCDCl₃+DMSO-d₆ w/TMS, ppm): 51.92 (quartet, OCH₃, ¹J_(CH)=147 Hz), 120.50(d, C4, C6, ¹J_(CH)=164.4 Hz), 121.10 (d, C2, ¹J_(CH)=168.3 Hz), 131.15(s, C1, C3), 157.36 (s, C5), 165.85 (s, COOR); GC-MS (in acetone): 210(M⁺).

[0023] To a 150-mL round-bottom flask equipped with a magnetic stirringbar were added dimethyl 5-hydroxyisophthalate, N,N-dimethylthiocarbamoylchloride, DABCO (1 ,4-diazabicyclo[2.2.2]octane), and 50 mL ofN,N-dimethylformamide. The mixture was stirred at room temperature for 5hours, and 100 mL of water then was added slowly. The orange solidgradually disappeared, and the solution became light brown. Anadditional 100 mL of water was added to induce the precipitation of awhite solid, which was filtered off and washed on the filter withportions of water until the pH of the wash liquid was neutral. Theproduct was dried, preferably under vacuum at 60° C. overnight, to give1-0-3,5-bis(methoxycarbonyl)phenylene N,N-dimethylthiocarbamate as awhite powder. Testing of the compound revealed the following: mp114.5-116.5° C.; ¹H NMR (in CDCl₃w/TMS, ppm): 3.38 (s, 3H, NCH₃), 3.46(s, 3H, NCH₃), 3.94 (s, 6H, OCH₃), 7.93 (s, 2H, CH), 8.58 (s, 1H, CH);{¹H}¹³C NMR (in CDCl₃w/TMS, ppm): 38.85 (NCH₃), 43.39 (NCH₃), 52.51(OCH₃), 127.96 (C4), 128.36 (C2, C6), 131.54 (C3, C5), 153.86 (C1),165.30 (COOR), 186.84 (OC(S)NR₂).

[0024] As shown by the following table, reaction yield for1-O-3,5-bis(methoxycarbonyl)phenylene N,N-dimethylthiocarbamate variedas a function of the molar ratio of the reactants. TABLE 1 Molar Ratioof the Reactants vs. Reaction Yield N,N-Dimethyl- Dimethyl thiocarbamoylEster a Chloride, DABCO, Yield, g (mmol) g (mmol) g (mmol) Molar Ratio g(%) 5.50 (26.2) 9.60 (77.0) 8.70 (77.0) 1/3/3 7.60 (97.7) 5.00 (23.8)3.30 (26.2) 8.00 (71.4) 1/1.1/3 6.54 (92.5) 5.00 (23.8) 3.30 (26.2) 5.34(47.6) 1/1.1/2 6.42 (90.7) 5.00 (23.8) 2.95 (23.8) 2.95 (26.3) 1/1/1.15.13 (72.4) 4.82 (22.9) 3.12 (25.2) 3.86 (34.4) 1/1.1/1.5 4.38 (64.0)

[0025] In a test tube containing a magnetic stirring bar, 0.1 g (0.336mmol) of 1-O-3,5-bis(methoxycarbonyl)phenylene N,N-dimethylthiocarbamatewas heated constant temperature, preferably about 230-235° C., for aferably at least 20 minutes. As can be seen from the action yield variedas a function of time and temperature. TABLE 2 Reaction Yield of1-S-3,5-bis(methoxycarbonyl)phenlylene N,N- dimethylthiocarbamate As aFunction of Temperature and Time Temperature, ° C. Time, min Yield,%^(a) 176  20 No reaction 200  20  <5 208  20  <5 220  20    30 230  20   55 240  20 Decomposition 230  40    75 230  60    90 232  60  >90 232 90    95 232-235  60   100 232-235  90   100 232-236 120   100

[0026] The white solid first melted into a yellowish oil, then graduallybecame dark brown. After cooling to room temperature, a tar-like solidwas obtained. Recrystallization from methanol gave1-S-3,5-bis(methoxycarbonyl)phenylene N,N-dimethylthiocarbamate as agray solid having the following characteristics: mp 117-118° C.; ¹H NMR(in CDCl₃w/TMS, ppm): 3.06 (s, 3H, NCH₃), 3.12 (s, 3H, NCH₃), 3.94 (s,6H, OCH₃), 8.34 (s, 2H, CH), 8.69 (s, 1H, CH); {¹H}¹³C NMR (in CDCl₃w/TMS, ppm): 37.06 (N(CH₃)₂), 52.53 (OCH₃), 130.90 (C4), 131.44 (C3,C5),131.58 (C2, C6),140.87 (C1), 165.81 (COOR), 165.94 (SC(O)NR₂);¹H-¹³C NMR (in CDCl₃ w/TMS, ppm): 37.06 (quartet, N(CH₃)₂, ¹J_(CH)=139.6Hz), 52.53 (quartet, OCH₃, ¹J_(CH)=147.34 Hz), 130.90 (doublet oftriplets, C4, ¹J_(CH)=167.65 Hz, ³J_(CH=6.448) Hz), 131.44 (C3,C5),131.58 (doublet of doublets, C2, C6, ¹J_(CH)=168.3 Hz, ³J_(CH)=6.448Hz),140.87 (C1), 165.81 (COOR), 165.94 (SC(O)NR₂).

[0027] The 1-O-3,5-bis(methoxycarbonyl)phenylene N,N-dimethylthiocarbamate (112.2 g, 0.377 mol) was placed in a 2-L two-neckedround-bottom flask equipped with a magnetic stirring bar, a condenser,and a thermometer. The flask was submerged in an oil bath preheated to232-234° C. and kept at that temperature for 2 hours. The resulting darkbrown oil was allowed to cool to about 80° C. Then the thermometer wasreplaced by a gas inlet tube, and the system was purged with nitrogenbefore 850 mL of 2.7 N NaOH was added. The mixture was heated underreflux for 2 hours, cooled to room temperature, and acidified to pH<4with 10% aqueous HCl. Then the beige solid product was washed,preferably 3 times, with 400-mL portions of water and dried under vacuumat 60-70° C. to obtain 5-mercaptoisophthalic acid. Testing of thecompound revealed the following properties: yield 67.5 g (90.3%); mp240-246° C.; ¹H NMR (in DMSO-d₆w/TMS, ppm): 3.02 (s, 1H, SH), 8.24 (s,2H, CH), 8.37 (s, 1H, CH), 13.50 (broad, 2H, COOH); {¹H}¹³C NMR (inDMSO-d₆ w/TMS, ppm): 129.43 (C2),130.88 (C4, C6),134.74 (C1, C3),136.51(C5), 166.91 (COOH); ¹H-¹³C NMR (in DMSO-d₆w/TMS, ppm): 129.43 (d, C2,¹J_(CH)=167.39 Hz), 130.88 (d, C4, C6, ¹J_(CH=165.27) Hz), 134.74 (C1,C3),136.51 (C5),166.91 (COOH).

[0028] In the final step of the synthesis, to a 1-L round-bottom flaskequipped with a magnetic stirring bar, a water separator, and acondenser were added 65.1 g (0.328 mol) of powdered5-mercaptoisophthalic acid, 113 mL (94.2 g, 0.723 mol) of2-ethyl-1-hexanol, 200 mL of benzene, and 4 mL of concentrated H₂SO₄.After the mixture had been heated under reflux for a sufficient time,approximately 3 h, about 12 mL (0.67 mol) of water had been collected bythe water separator. The mixture was allowed to reflux until all of thesolid was dissolved, generally about 24 hours, and a dark brown solutionwas obtained. After cooling to room temperature, the solution was pouredinto ice water, and the organic layer was washed in succession with 50mL of saturated NaHCO₃ solution and two 50-mL portions of water. Theorganic layer was dried over anhydrous MgSO₄, and the dried solution wasdecolorized with ca. 10 g of activated carbon. After filtration, most ofthe benzene was removed by distillation at atmospheric pressure, and theexcess 2-ethyl-1-hexanol and a trace amount of benzene were then removedby distillation at about 1 torr. The residual oil was bis(2-ethylhexyl)5-mercaptoisophthalate. Testing on the compound revealed the followingdata: yield 132.7 g (95.5%); GC purity>89%; ¹H NMR (in CDCl₃w/TMS, ppm):0.94 (m, 8H, CH₂), 1.40 (m, 20H, CH₂CH₃), 1.75 (m, 2H, CH), 3.77 (s, 1H,SH), 4.28 (d, 4H, CH₂),8.11 (s, 2H, CH), 8.43 (s, 1H, CH); {¹H}¹³C NMR(in CDCl₃ w/TMS, ppm): 11.125 (C6′/C8′), 14.031 (C6′/C8′), 23.050(C5′/C7′), 24.211 (C5′/C7′), 29.154 (C3′/C4′), 30.760 (C3′/C4′),39.196(C2′), 68.107(C1′), 127.87(C2),132.23(C1,C3),133.09 (C5),134.14(C4, C6),165.47 (COOR); GC-MS (in acetone): 422 (M⁺).

[0029] The reaction sequence for the synthesis just described is asfollows:

[0030] The organic thiol compounds disclosed by the present inventioncan be used as additives for polymeric compounds, wherein, for example,the organic thiols can serve as plasticizers as well as stabilizers. Theorganic thiols are free of metal, and are not used in conjunction withany other metal-based stabilizers or Lewis acids. By metal-basedstabilizers it is meant any metal compound, salt, complex, or the likeof any of the metals as set forth in groups 1-8 of the periodic tablesuch as, but not limited to the heavy metals, for example cadmium,mercury, lead, and the like as well as other generally environmentallyunfriendly or undesirable compounds. Examples of specific metal-basedstabilizers which are avoided include those set forth in European PatentApplication EP 0 945 484 A1 at least on page 3 thereof. Thesubstantially free amount of the various metal-based stabilizers isgenerally less than about 2 percent, desirably less than about 1percent, and preferably less than about 0.5 percent by weight based upon100 total parts by weight of the one or more halogen-containing polymersor copolymers. The polymer compositions of the present invention arealso generally substantially free of various Lewis acids such as borontrifluoride, aluminum chloride, zinc chloride, methyltin trichloride,dibutyltin dichloride, and the like. Such acids when contained in thepolymeric composition are generally less than about 0.5 percent,desirably less than about 0.1 percent, and preferably less than about0.01 percent by weight per 100 total parts by weight of allhalogen-containing polymers or copolymers.

[0031] The polymers utilized in the present invention include anyorganic chlorine- or bromine-containing polymers or resins in which thehalogen is attached directly to a carbon atom. Polymers and/or monomersthereof useful to the present invention include, but are not limited to,poly(vinyl chloride) (PVC), poly(vinylidene chloride), poly(vinylbromide), poly(vinylidene bromide), chlorinated poly(vinyl chloride),chlorinated polyethylene, chlorinated natural or synthetic rubber,polychloroprene, rubber hydrochloride, or chlorinated polystyrene, andcombinations and copolymers thereof. The molecular weight of suchpolymers can vary over a wide range, and they can have a number averagemolecular weight of from about 5,000 to about 1,000,000. Such polymerscan also contain other plasticizers in addition to the compounds of thepresent invention, and where appropriate, such polymers can beplastisols, organisols, and the like.

[0032] The above noted chlorine- or bromine-containing polymers are madefrom monomers forming the same such as vinyl chloride, vinylidenechloride, and the like, or are a copolymer made from a mixture ofmonomers comprising, desirably, at least about 70% by weight of vinylchloride, based on the total monomer weight. Examples of the copolymersinclude those made from vinyl chloride and from about 1 to about 30% ofa copolymerizable ethylenically unsaturated monomer such as vinylacetate, vinyl butyrate, vinyl benzoate, vinylidene chloride, diethylfumarate, diethyl maleate, other alkyl fumarates and maleates, vinylpropionate, methyl acrylate, 2-ethylhexyl acrylate, butyl acrylate andother alkyl acrylates, methyl methacrylate, ethyl methacrylate, butylmethacrylate and other alkyl methacrylates, methyl alpha-chloroacrylate,styrene, trichloroethylene, vinyl ethers such as vinyl ethyl ether,vinyl chloroethyl ether and vinyl phenyl ether, vinyl ketones such asvinyl methyl ketone and vinyl phenyl ketone, 1-fluoro-2-chloroethylene,acrylonitrile, chloroacrylonitrile, allylidene diacetate andchloroallylidene diacetate. Typical copolymers include vinylchloride-vinyl acetate (e.g. 96:4 sold commercially as VYNW), vinylchloride-vinyl acetate (e.g. 87:13), vinyl chloride-vinyl acetate-maleicanhydride (e.g. 86:13:1), vinyl chloride-vinylidene chloride (e.g.95:5), vinyl chloride-diethyl fumarate (e.g. 95:5), and vinylchloride-2-ethylhexyl acrylate (e.g. 80:20).

[0033] Preferred polymers include poly(vinyl chloride) and poly(vinylbromide). Preferred copolymers include vinyl chloride-vinyl acetate,vinyl chloride-vinylidene chloride, and other vinyl chloride copolymers.

[0034] The organic thiol compounds according to the present inventioncan be added to or blended with the above described polymers in anysuitable amount, generally from about 1 to about 100 parts by weight per100 total parts by weight of all of the one or more polymers orcopolymers, depending on the desired properties of the final product. Asstated above, the organic thiol compounds of the present invention areparticularly suitable for serving as both stabilizers and plasticizers.A semi-rigid composition of the present invention would desirablycontain from about 1 to about 25 parts of the organic thiol compound per100 parts by weight of a polymer defined above. A flexible compositionof this invention contains from about 25 to about 100 parts of theorganic thiol compound per 100 parts of polymer utilized in the presentinvention. The organic thiol compounds can be incorporated into theresin by any one of many known methods that provide for uniformdistribution of additives throughout resin compositions, such as, forexample, mixing in an appropriate mill, mixer, or Banbury apparatus.

[0035] Depending on the end use, further additives, known to the art andto the literature or to those of ordinary skill in the art, can be addedin conventional amounts to the above noted polymers, such as certainother stabilizers and costabilizers, lubricants, plasticizers,extenders, impact modifiers, fillers, pigments, antioxidants, dyes,ultraviolet light absorbing agents, densifying agents, and the like.

[0036] As stated above, the organic thiols greatly enhance the heatstability of halogenated resins, which are known to undergo rapidthermal degradation under the conditions found in the processes to whichthese resins are subjected, such as, for example, calendering,extrusion, injection molding, and end usage at elevated temperatures.For example, poly(vinyl chloride) is known to undergo a rapid andsequential elimination of hydrogen chloride, or dehydrochlorination, atelevated process temperatures. Other halogenated resins are known toundergo similar dehydrohalogenation reactions. Dehydrochlorination inPVC can initiate at labile chlorines that are associated withirregularities in the molecular chain, such as branches or double bonds.Once free, the HCI promotes further degradation of the poly(vinylchloride) through unzipping of additional hydrogen chloride from thepolymer chain. The primary functions of heat stabilizers in PVC are todepress hydrogen chloride elimination and discoloration. In addition tofunctioning as heat stabilizers, the organic thiols of the presentinvention are often effective plasticizers and frequently serve orfunction as both a heat stabilizer and a plasticizer. Thus, in manypolymer compositions such as PVC, organic thiols of the presentinvention serve as heavy-metal-free or metal-based-free stabilizers andplasticizers, a unique combination.

[0037] The organic thiols of the invention thus unexpectedly improve theprocessing properties of the polymers, further providing cost andefficiency improvements to resin processors. The disclosed thiols alsoreduce odor problems associated with the processing of resins stabilizedthereby and provide increased resistance to resin yellowing associatedwith thermal degradation.

[0038] The following examples serve to illustrate, but not to limit, thepresent invention.

EXAMPLES Example 1

[0039] An intimate mixture of PVC and di(2-ethylhexyl)5-mercaptoisophthalate (0.044 mole per mole of PVC monomer units) washeated under argon at 170° C. for 1.5 hours. At the end of the heatingperiod, the mixture retained its initial white color.

Example 2 Control

[0040] An intimate mixture of PVC and 1-dodecanethiol (0.044 mole permole of PVC monomer units) was heated under argon at 170° C. for 1.5hours. At the end of the heating period, the mixture was dark red-brownin color, a result that was indicative of extensive degradation.

[0041] The following Table 3 is a comparative evaluation of the organicthiol bis(2-ethylhexyl) 5-mercaptoisophthalate in a typical poly(vinylchloride) composition with current commercially utilized stabilizers.The formulations evaluated (A-F) were prepared by standard blendingmethods that are well-known to those skilled in the art. Properties ofthese formulations were determined by the standard ASTM methods that areidentified under the heading “Test Description”. The measurementsreported show that the thiol plasticizer/stabilizer gave physicalproperties to the formulations which were comparable to those obtainedwith the common commercial plasticizer, DOP. Thus it is apparent thatthe thiol can function as the primary plasticizer for PVC without theneed for additional plasticization. Moreover, the data in Table 3 showthat the dynamic and static heat stability conferred by the thiol areequal to or better than those obtained with traditional amounts ofcommercial lead or barium-zinc heat stabilizers. Further, the tabulateddata reveal that the stability obtained with the thiol can be achievedwithout the incorporation of an epoxidized soybean oil costabilizer.Finally, the data for formulations E and F indicate that the thermalstabilization effects of the thiol and the barium-zinc stabilizer areantagonistic, rather than additive or synergistic. TABLE 3 Evaluation ofBis(2-ethylhexyl) 5-Mercaptoisophthalate in a Typical Poly(vinylchloride) Composition Ingredient Description A(control) B(control) C D EF Oxyvinyl 455F (PVC) 100.00 100.00 100.00 100.00 100.00 100.00 DOP(Plasticizer) 30.00 30.00 — — — 30.00 Thiol Plasticizer/Stabilizer(Bis(2-ethylhexyl) 5- — — 35.00 30.00 30.00 5.00 mercaptoisophthalate)Epoxidized Soybean Oil (HCI scavenger) 5.00 5.00 — 5.00 5.00 — GeneralPurpose Ba/Zn Liquid (Stabilizer) 3.00 — — — 3.00 3.00 Dythal/TribaseBlend (Lead stabilizer) — 4.00 — — — — Stearic Acid (Processinglubricant) 0.10 0.10 0.10 0.10 0.10 0.10 Total (Parts by weight) 138.10139.10 135.10 135.10 138.10 138.10 Test Description A B C D E FHardness, Shore C (ASTM D 2240-86) 85/74 86/75 94/85 94/86 95/91 86/75Specific Gravity (ASTM D 792-91) 1.27 1.3 1.29 1.29 1.29 1.27 TensileStrength, PSI (ASTM D 638-91) 3315 3472 3467 3421 3218 3322 Elongation,% (ASTM D 638-91) 338 305 281 328 306 341 Dynamic Heat Stability, 205°C., 100 RPM, 24 60 60 60 60 3 #5 Bowl, Min (ASTM D 2538-95) InitialYellow, 210° C., Min (ASTM D 2538-95) 15 10 10 10 15 15 DecompositionTime, 210° C., Min 45 >60 >60 >60 25 20 (ASTM D 2115-92)

[0042] In accordance with the patent statutes, the best made andpreferred embodiments have been set forth, and the scope of the presentinvention is not limited thereto, but rather by the scope of theattached claims.

What is claimed is:
 1. An organic thiol compound having the formulacomprising:

wherein, independently, R¹ and R² comprise straight chain or branchedalkyls having from 1 or 2 to about 15 carbon atoms, or an aromatic or asubstituted aromatic having from about 6 to about 15 carbon atoms, andwherein, independently, n is either 0, 1, 2, or 3, m is either 0, 1, 2,or 3, and p is either 0, 1, 2, or 3, with the proviso that m+n+p=6 orless, wherein when, independently, m, n, and/or p are greater than 1,the individual repeat groups are each attached to a different carbonatom on the benzene ring.
 2. An organic thiol compound according toclaim 1, wherein R¹ and R², independently, comprise straight chain orbranched alkyls having from about 4 carbon atoms to about 15 carbonatoms.
 3. An organic thiol compound according to claim 1, wherein R¹ is2-ethylhexyl, m is 0, n is 1 and p is
 2. 4. An organic thiol compoundaccording to claim 1, wherein m is 0, n is 1 and p is 1 or
 3. 5. Anorganic thiol compound according to claim 1, wherein m is
 0. 6. Apolymer composition comprising: a chlorine-containing orbromine-containing polymer; and an organic thiol compound having theformula:

wherein R¹ and R², independently, comprise straight chain or branchedalkyls having from 1 or 2 to about 15 carbon atoms, or an aromatic or asubstituted aromatic having from about 6 to about 15 carbon atoms, andwherein, independently, n is either 0, 1, 2, or 3, m is either 0, 1, 2,or 3, and p is either 0, 1, 2, or 3, with the proviso that m+n+p=6 orless, wherein when, independently, m, n, and/or p are greater than 1,the individual repeat groups are each attached to a different carbonatom on the benzene ring, said organic thiol compound being present inan amount from about 1 to about 100 parts per 100 parts by weight ofsaid polymer, and said composition being substantially free of ametal-based stabilizer.
 7. A polymer composition according to claim 6,wherein R¹ and R², independently, comprise straight chain or branchedalkyls having from about 4 carbon atoms to about 15 carbon atoms.
 8. Apolymer composition according to claim 6, wherein R¹ is 2-ethylhexyl, mis 0, n is 1 and p is
 2. 9. A polymer composition according to claim 6,wherein m is 0, n is 1 and p is 1 or
 3. 10. A polymer compositionaccording to claim 6, wherein said polymer is poly(vinyl chloride),poly(vinylidene chloride), poly(vinyl bromide), poly(vinylidenebromide), chlorinated poly(vinyl chloride), chlorinated polyethylene,chlorinated natural or synthetic rubber, polychloroprene, rubberhydrochloride, chlorinated polystyrene, or copolymers thereof, orcombinations thereof.
 11. A polymer composition according to claim 10,wherein m is
 0. 12. A halogen-containing polymer composition,comprising: an organic thiol compound; and at least onehalogen-containing polymer, wherein said organic thiol is an aromaticcompound having at least one sulfhydryl group attached indirectly ordirectly to an aromatic ring, and wherein said composition issubstantially free of a metal-based stabilizer.
 13. A compositionaccording to claim 12, wherein said polymer is a chlorine-containingpolymer, or a bromine-containing polymer, or combinations thereof.
 14. Acomposition according to claim 13, wherein the amount of said organicthiol compound is from about 1 to about 100 parts by weight per 100parts by weight of said halogen-containing polymer, and wherein saidpolymer is poly(vinyl chloride), poly(vinylidene chloride), poly(vinylbromide), poly(vinylidene bromide), chlorinated poly(vinyl chloride),chlorinated polyethylene, chlorinated natural or synthetic rubber,polychloroprene, rubber hydrochloride, or chlorinated polystyrene, orcopolymers thereof, or combinations thereof.
 15. A composition accordingto claim 14, wherein said organic thiol has the formula:

wherein, independently, R¹ and R² comprise straight chain or branchedalkyls having from 1 or 2 to about 15 carbon atoms, and wherein,independently, n is either 0, 1, 2, or 3, m is either 0, 1, 2, or 3 andp is either 0, 1, 2, or 3, with the proviso that m+n+p=6 or less,wherein when, independently, m, n, and/or p are greater than 1, theindividual repeat groups are each attached to a different carbon atom onthe benzene ring.
 16. A composition according to claim 15, wherein saidorganic thiol is:

, or combinations thereof.
 17. A composition according to claim 16,wherein said polymer is poly(vinyl chloride), poly(vinyl bromide), orcombinations thereof, and wherein said organic thiol compound is:


18. A composition according to claim 17, wherein the amount of saidorganic thiol is from about 2 to about 50 parts by weight per 100 partsby weight of the total polymers.
 19. A composition according to claim12, wherein said composition contains about 2 parts by weight or less ofa metal-based stabilizer per 100 parts by weight of said of at least onehalogen-containing polymer.
 20. A composition according to claim 16,wherein said composition contains about 0.5 parts by weight or less of ametal-based stabilizer per 100 parts by weight of said of at least onehalogen-containing polymer.
 21. A plasticizer-stabilizer comprising thecomposition of claim
 1. 22. A plasticizer-stabilizer comprising thecomposition of claim
 2. 23. A plasticizer-stabilizer comprising thecomposition of claim
 3. 24. A plasticizer-stabilizer comprising thecomposition of claim
 4. 25. A plasticizer-stabilizer comprising thecomposition of claim 5.